1. Field of the Invention
The present invention relates to a time-domain temperature sensing system with a digital output and method thereof. More particularly, the present invention relates to the time-domain temperature sensing system and method providing a simplified structure.
2. Description of the Related Art
TAIWANESE PATENT PUBLICATION No. I275782, entitled “DIGITAL TEMPERATURE SENSING SYSTEM”, discloses a temperature sensing system which is operated for converting a temperature into a corresponding digital signal. The temperature sensing system includes a temperature sensor and a time-to-digital conversion circuit. The temperature sensor is provided for generating a time signal varying with the temperature. The time-to-digital conversion circuit electrically connects with the temperature sensor for converting the time signal into the corresponding digital signal.
Another TAIWANESE PATENT PUBLICATION No. I355485, entitled “TIME DOMAIN DIGITAL TEMPERATURE SENSING SYSTEM AND METHOD THEREOF”, discloses an apparatus and method for converting a temperature into a corresponding digital signal. The apparatus includes a temperature-to-time conversion circuit, an adjustable time reference circuit, a time comparator, a control logic circuit and a digital output. The temperature-to-time conversion circuit is provided for sensing the temperature to generate a thermally sensitive time signal with a width proportional to the sensed temperature. The adjustable time reference circuit is provided for digital coding to generate a low thermally-sensitive time signal with a reference time width controlled by a digital input. The time comparator is provided for comparing the two time signals to generate a time comparison output. The control logic circuit is provided to adjust the delay of the adjustable time reference circuit according to the time comparison output to allow the widths of the two time signals to approach approximately. The digital input connects with the digital input of the adjustable time reference circuit and is further assigned to be an output of the temperature sensing system.
However, the digital temperature sensing systems disclosed in TAIWANESE PATENT PUBLICATION Nos. I275782 and I355485 are complicated. Hence, there is a need of improving the digital temperature sensing systems with a simplified circuit. The above-mentioned patents and publications are incorporated herein by reference for purposes including, but not limited to, indicating the background of the present invention and illustrating the state of the art.
As is described in greater detail below, the present invention provides a time-domain temperature sensing system with a digital output and method thereof. A cyclic delay line is applied to sense a temperature and to measure a pulse width, and a path selection circuit is provided to effectively utilize components of the cyclic delay line in such a way to mitigate and overcome the above problem.